A thermal type air flow sensor that measures a flow rate of air is configured to include a flow detecting unit for measuring an air flow rate and to measure the air flow rate of a gas by causing thermal transfer between the flow detecting unit and the gas as a measurement target. The air flow rate measured by the thermal type air flow sensor is widely used as a significant control parameter in various apparatuses. The thermal type air flow sensor is distinctive in that the air flow rate can be measured with relatively high accuracy, compared to a flow sensor using another method.
However, it is desirable to achieve further improved accuracy in the air flow rate measurement. For example, in a vehicle on which an internal combustion engine is mounted, low fuel consumption or exhaust gas purification is highly demanded. In response to the demands, it is required to measure air intake as a principal parameter of the internal combustion engine with high accuracy. The thermal type air flow sensor that measures the air intake of air guided to the internal combustion engine includes a sub passage through which a part of the air intake flows and a flow detecting unit disposed on the sub passage, measures a state of a measurement target gas which flows through the sub passage by thermal transfer performed by the flow detecting unit between the measurement target gas and the flow detecting unit, and outputs an electrical signal representing the air intake guided into the internal combustion engine. For example, JP-A-2011-252796 (PTL 1) discloses such a technology.